/*
 * Copyright (c) 2013, SRI International
 * All rights reserved.
 * Licensed under the The BSD 3-Clause License;
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 * 
 * http://opensource.org/licenses/BSD-3-Clause
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 
 * Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 
 * Neither the name of the aic-expresso nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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package com.sri.ai.grinder.library.lambda;

import java.util.Iterator;
import java.util.List;

import com.google.common.annotations.Beta;
import com.sri.ai.expresso.api.Expression;
import com.sri.ai.grinder.api.RewritingProcess;
import com.sri.ai.grinder.core.AbstractRewriter;
import com.sri.ai.grinder.library.Substitute;

/**
 * 
 * @author braz
 *
 */
@Beta
public class LambdaApplication extends AbstractRewriter {
	public interface PerformApplication {
		boolean isApplicationToBePerformed(Expression lambdaExpression, RewritingProcess process);
	}
	
	private PerformApplication performApplication = null;
	
	public LambdaApplication() {
		this(new PerformApplication() {
			@Override
			public boolean isApplicationToBePerformed(Expression lambdaExpression, RewritingProcess process) {
				// By default always perform
				return true;
			}
		});
	}
	
	public LambdaApplication(PerformApplication performApplication) {
		this.performApplication = performApplication;
	}

	@Override
	public Expression rewriteAfterBookkeeping(Expression expression, RewritingProcess process) {
		Expression functor = expression.getFunctor();
		if (Lambda.isLambdaExpression(functor) &&
			performApplication.isApplicationToBePerformed(functor, process)) {
			List<Expression> parameters = Lambda.getParameters(functor);
			if (parameters.size() != expression.numberOfArguments()) {
				throw new Error("Lambda application number of parameters and arguments does not match: " + expression);
			}
			Expression result = Lambda.getBody(functor);
			Iterator<Expression> parameterIterator = parameters.iterator();
			Iterator<Expression> argumentIterator = expression.getArguments().iterator();
			while (parameterIterator.hasNext()) {
				Expression parameter = parameterIterator.next();
				Expression argument = argumentIterator.next();
				result = Substitute.replace(result, parameter, argument, true, process);
			}
			return result;
		}
		return expression;
	}
}
